don’t worry about that… it is asking for your number so it can send APP to you phone …
i know deep down you are not a dumb..so stop acting like ! …read the steps by OP carefully !
skip that step…you will see option in bottom ..!
rather Download their app from given link below:
https://apkpure.com/smartline-second-phone-number/com.godaddy.gdm.smartline
Those who unable to sign up on godaddy here is the GIF
!